Sensors exist for detecting a variety of quantities, such as speed, acceleration, temperature, pressure, light, motion, magnetic field, etc. Some existing sensors such as the Bosch SMB380 accelerometer allow their measurement ranges to be set by a user who performs an adjustment operation to set a relatively static range. Once set, the sensor uses the range to detect a phenomenon/circumstance specific to the sensor.
Numerous mechanical and electrical devices, from automobiles to cellular phones, use some kind of sensor or sensors. Depending on the application, different sensor measurement ranges and offsets may be of interest. For example, a movement detection application may care about sensor readings around some threshold of interest. Values significantly below or above the threshold may be irrelevant to the application, but readings in the immediate vicinity of the threshold may need to be known precisely.
With today's sensors, measurement precision is typically determined by the sensor output bitwidth (which is a function of an analog-to-digital converter (ADC) in digital sensors) and the measurement range that the sensor is programmed to cover. For example, typical ranges for an accelerometer are between −2 g and +2, between −4 g and +4 g and between −8 g and +8 g. Movement detection application sensors may have measurement precision on the order of mg. With today's sensor designs, however, assuming a 6-bit output and a range of +/−2 g, the measurement precision becomes 4 g/64=g/16 or on the order of tens to a hundred mg, thus a lot less accurate than desired.
Sensor parameters are typically trimmed during production according to customer needs. In other cases, the sensor parameters could be customized by the user by choosing nominal values of certain electronic components (e.g., capacitors and/or resistors) external to the sensor's hardware. The sensor parameters remained constant through the operation cycle, or even through the lifetime of the device.
Sensors are now featuring customizable “on the fly” parameters that the user may change when needed, by sending a re-configuration command to the sensor. For example, magnetic compasses commonly have measurement range around 0.7 Gauss, which is the maximum Earth Magnetic field. Single-range compasses are designed with a wider range (typically 2-6 Gauss) to accommodate for the possible compass proximity to metal objects, inside the device or outside of it. Many state of the art compasses are featuring user-selectable measurement ranges. As further examples, to accommodate different motion modes, accelerometers are often designed with user-selectable ranges, such as 2 g, 4 g, 8 g, and gyroscopes are often designed with user-selectable ranges of 100 degrees per second and 300 degrees per second.
For sensors featuring configurable measurement ranges, the ranges are normally set by the application to as narrow as possible for the given mode. This is because the sensor error (noise, offset, drift, quantization error for digital sensors) does not typically depend on the measured parameter value, but rather on the sensor measurement range. Sometimes the error is directly proportional to the measurement range, or even if it is not, the error will be higher at a wider measurement range. Thus reducing the range will usually result in the reduction of the measurement error. The ranges, however, are set to the widest range for the given mode, and for multiple modes if the mode of use is not known in advance.